Vibration-decoupled pulley having an integrated visco damper

ABSTRACT

A pulley ( 1 ) that is decoupled from the vibrations of a crankshaft and that has an integrated viscous torsional vibration damper ( 2 ), including a flywheel ( 3 ), which is arranged in a damper housing ( 5 ) that is filled with a viscous medium ( 4 ) and which can rotate relative to the housing, as well as a bearing ( 6 ) and a coupling ( 7 ) made of rubber elastic material, for supporting the pulley ( 1 ) with respect to the damper housing ( 5 ) in a flexible manner in the circumferential direction of the pulley and so as to be capable of relative rotation, the pulley ( 1 ) being assigned to the flywheel ( 3 ) so as to be axially adjoining. The damper housing ( 5 ) has at least one first axial projection ( 8 ), which is enclosed by the belt-bearing surface ( 9 ) of the pulley ( 1 ) at a radial clearance, and the bearing ( 6 ) is arranged in the gap ( 10 ) that is formed by the clearance.

DESCRIPTION

[0001] 1. Technical Area

[0002] The present invention relates to a pulley that is decoupled fromthe vibrations of a crankshaft and that has an integrated viscoustorsional vibration damper, including a flywheel, which is arranged in adamper housing that is filled with a viscous medium and which can rotaterelative to the housing, as well as a bearing and a coupling made ofrubber elastic material, for supporting the pulley in relation to thedamper housing in a flexible manner in the direction of thecircumference of the pulley and so as to be capable of relativerotation, the pulley being arranged so as to be axially adjacent to theflywheel.

[0003] A visco damper in the context of the present invention isunderstood as a viscocity torsional vibration damper.

[0004] 2. Background Information

[0005] In this context, a pulley of this type is known from GermanPatent Application No. 197 08 082 A1. A hub and a separately produceddamper housing, are fixedly connected to the crankshaft of an internalcombustion engine, the damper housing, in FIGS. 1 and 3, being radiallyenclosed on the exterior side by a first belt-bearing surface of thepulley at a radial clearance, a sliding bearing being arranged in thegap formed by the clearance. The bearing contacts the externalcircumference of the damper housing and the internal circumference ofthe first belt-bearing surface, immediately adjacent. The couplingconnects the hub to a second belt-bearing surface, which is assigned tothe first belt-bearing surface so as to be one integrated piece, axiallyadjacent. In FIG. 2, the pulley is supported on the hub by a bearing,the elastic flexibility of the pulley in the circumferential directionwith respect to the hub being effected by the coupling.

PRESENTATION OF THE INVENTION

[0006] The present invention is based on the objective of furtherdeveloping a pulley of the type cited above, such that the bearingprovided for the rotationally flexible support of the pulley, duringnormal use, is subjected to comparatively quite reduced temperatures andtherefore has improved working properties during a significantlylengthened service life. In addition, the decoupled pulley has a simplerand more cost-effective design and is easier to assemble. Furthermore,the available installation space for the largest possible exteriordiameter of the visco damper is not hemmed in by the pulley.

[0007] This objective is achieved according to the present inventionthrough the features of claim 1. The subclaims refer to advantageousembodiments.

[0008] In the context of the present invention, it is provided forachieving the objective that the damper housing has at least one firstaxial projection, which is enclosed by the belt-bearing surface of thepulley at a radial clearance and that the bearing is arranged in the gapformed by the clearance. Pulleys having integrated torsional vibrationdampers are generally provided, on the one hand, to decouple throughvibration technology the belt drive of the auxiliary aggregates from therotational irregularities of the crankshaft driving the auxiliaryaggregates, and, on the other hand, to dampen the torsional vibrationsof the crankshaft. The belt drive is decoupled, through vibrationtechnology, as a result of the torsionally flexible coupling that ismade of rubber elastic material, and the torsional vibrations of thecrankshaft are dampened by the visco damper. In comparison toconventional vibration dampers, in which a flywheel surrounds a hub ringat a radial clearance, a spring member made of rubber elastic materialbeing arranged in the gap formed by the clearance, visco dampers havethe advantage of a greater working capacity. The flywheel of the viscoustorsional vibration damper is arranged in the damper housing, where aviscous damping medium is situated within an annular gap between theflywheel and the damper housing. To dampen torsional vibrations, forexample, of a crankshaft, the flywheel within the damper housing canrotate freely in the circumferential direction, a dampening effect beinggenerated by the rotatability of flywheel and damper housing relative toeach other and by the alternating shearing of the viscous medium withinthe annular gap. In this manner, mechanical energy is converted intoheat, which can be removed via the damper housing surrounding theflywheel. In this context, temperatures of, for example, 110 degrees C.can arise on the surface of the damper housing. The axially adjacentarrangement of pulley and visco damper makes it possible to optimallyexploit the available installation space with regard to the achievablesupport and damping characteristics.

[0009] The working capacity of the visco damper is substantiallydetermined by the rotational mass of the flywheel. The greatest possibleexterior diameter of the visco damper should therefore be the goal, ifthere is high torsional stressing. As a result of the embodimentaccording to the present invention, the available installation space ofthe visco damper is not hemmed in by the pulley.

[0010] In the configuration of the pulley in accordance with the presentinvention, it is advantageous that the visco damper is spatiallyseparated from the pulley bearing so that, even in response to highthermal stressing of the visco damper, no undesirable increase intemperature is created in the bearing; the danger of attenuated workingproperties as a result of excessive bearing temperatures is kept to aminimum.

[0011] If the bearing encloses, for example, the exterior circumferenceof the damper housing, as in the above-mentioned related art, then thebearing has a temperature that essentially corresponds to the surfacetemperature of the damper housing. In contrast, in accordance with thepresent invention, as a result of the arrangement of the bearing on thefirst axial projection, a reduction of the bearing temperature by atleast 15% is assured, in comparison to the surface temperature of thedamper housing.

[0012] Other improved working properties are achieved as a result of thefact that the dimensioning of the visco damper is not influenced by thepulley. As a result, a significantly more effective visco damper can beconfigured, which achieves a significantly lower temperature level incomparison to the related art, it being possible to achieve atemperature reduction greater than 50%. In critical applications, theuse of the visco damper is therefore made possible, since the maximumtemperature stressing of the visco damper is limited.

[0013] The aforementioned arrangement has a special advantage if thebearing is an unlubricated sliding bearing, as is generally customary inthese application cases.

[0014] The damper housing can be configured, for example, as a castpart. In this context, it is advantageous that the axial projection canbe pre-molded without difficulty onto the damper housing and that, as aresult of the manifold configuration possibilities of thevibration-decoupled pulley, component parts of this type can also beused in irregular installation spaces, which is of great importance.

[0015] It is also advantageous that by introducing appropriate openingsin the housing and the pulley, it is possible to ventilate the interiorspace between the coupling and housing, thus enabling the bearing anddamper to be cooled.

[0016] The first axial projection is preferably constituted as anintegral component part of the damper housing. In this context, it isadvantageous that the vibration-decoupled pulley overall has a simpledesign of few parts and that it is easy to assemble, which is importantfrom the production-technical and economic points of view. As a resultof the configuration of the axial projection being integrated in thedamper housing, the radial position of the pulley with regard to thedamper housing is always clearly stipulated.

[0017] Viewed in cross-section, the pulley can have an essentiallyC-shaped profile. On the basis of the profile that is axially open inthe direction of the flywheel, the pulley surrounds the axialprojection, the bearing with regard to the reduced mechanical stresses,preferably enclosing the first axial projection radially on the exteriorside and supporting the interior circumferential surface of thebelt-bearing surface. The mechanical stresses on the bearing are limitedby its comparatively large diameter.

[0018] On the radial interior side, the torsionally flexible couplingmade of rubber elastic material is preferably vulcanized on the radiallyinterior leg of the C-shaped pulley. On the exterior circumference, theradially interior leg is assigned to the adjoining interiorcircumferential surface of the first axial leg at a radial clearance.

[0019] As a result of the configuration of the first axial projectionintegrated in the damper housing, it is possible to do without the moreexpensive, separate production of the damper housing and of the firstaxial projection as well as the subsequent process of joining them toeach other.

[0020] The bearing is configured as a radial bearing, because the strandforces introduced by the belt-bearing surface are active basically inthis direction.

[0021] For some application cases, it can be advantageous if the bearingis configured as a combined radial and axial bearing. The axial part ofthe bearing preferably extends in the radial direction within theC-shaped profile of the pulley between the interior circumferentialsurface of the belt-bearing surface and the exterior circumferentialsurface of the first axial arm. In a configuration of this type, it isadvantageous that the axial bearing is arranged within the hollow spacethat is bordered by the pulley, and that the axial bearing is thereforewell protected from impurities that could limit its service life. Onlyin response to an axial displacement of the pulley with respect to thefirst axial projection, is it possible that the axially adjacentsurfaces of the axial bearing and the end face of the axial projectionbriefly contact each other.

[0022] The bearing is preferably configured as an unlubricated slidingbearing. In comparison to rolling bearings, sliding bearings havesmaller dimensions, specifically in the radial direction, which is ofsignificant advantage with regard to the difficult installationsituations of the decoupled pulley.

[0023] The coupling on the side radially facing away from the pulley canbe fixedly arranged on a second axial projection of the housing. Incomparison to embodiments in which the interior circumference of thetorsionally flexible coupling is supported, for example, on the exteriorcircumference of a hub, which is fixedly joined to the damper housing,the arrangement of the interior circumference of the coupling on thesecond axial projection of the damper housing is advantageous becauseonly the pulley, together with the coupling, needs to be joined to thedamper housing. A supplemental, separate assembly procedure for securingthe interior circumference of the coupling on the surface of a hub istherefore not necessary.

[0024] An imaginary radial plane can intersect the belt-bearing surface,the bearing, the first axial projection, and the coupling, in each case,in basically an axially centered fashion. In this context, it isadvantageous that the strand forces introduced via the belt-bearingsurface do not exert any torque on the respective component parts. As aresult of this advantageous arrangement, the wear on the individualparts is minimized, and the decoupled pulley has uniformly good workingproperties during a long service life.

BRIEF DESCRIPTION OF THE DRAWING

[0025] An exemplary embodiment of the present invention is furtherdiscussed below on the basis of the FIGURE.

DESIGN OF THE INVENTION

[0026] In the FIGURE, an exemplary embodiment of a vibration-decoupledpulley 1 having an integrated visco damper 2 is depicted.

[0027] In the exemplary embodiment depicted here, pulley 1, visco damper2, bearing 6, and coupling 7 constitute a pre-assemblable unit 13.

[0028] The damper housing is executed as a cast part in the exemplaryembodiments depicted here, damper housing 5 completely enclosingflywheel 3. The annular hollow space between the surface of flywheel 3and the walls that border the hollow space of damper housing 5 is filledwith viscous medium 4, for example, a silicon oil. Flywheel 3 can rotatefreely relative to damper housing 5, the damping of torsional vibrationsof the crankshaft being achieved by a shearing of viscous medium 4 inresponse to rotations of flywheel 3 relative to damper housing 5. Thehollow space is closed to the outside by a cover that is secured ondamper housing 5.

[0029] Coupling 7, which is made of a rubber elastic material, isprovided in order to isolate irregularities in the rotation of thecrankshaft from the belt drive of attached auxiliary aggregates.

[0030] For the support of pulley 1 on damper housing 5, the pulley beingconfigured in this exemplary embodiment in a C-shaped profile, a bearing6 is provided, which is configured in this exemplary embodiment as anunlubricated sliding bearing. The bearing includes a radial bearing andan axial bearing, the radial bearing, on the exterior circumferenceside, enclosing first axial projection 8, which is provided as anintegral part of damper housing 5, and supporting pulley 1 atbelt-bearing surface 9. Pulley 1, which is open on the flywheel side,encloses annular axial projection 8. To the outside, the pulley isradially supported on axial projection 8 by radial bearing 6. To theinside, axial projection 8 radially borders an annular gap at thesurface of pulley 1 that is facing it.

[0031] On the interior circumferential side, coupling 7 is vulcanizedusing a ring 15, ring 15 being stamped onto a seat of second axialprojection 12. Second axial projection 12, like first axial projection8, is an integral component part of damper housing 5.

[0032] An imaginary radial plane 14 intersects belt-bearing surface 9,bearing 6, first axial projection 8, and coupling 7, in each case,essentially in the axial center. As a result of the reciprocalassignment of the aforementioned component parts, the center of gravityof the respective parts lying essentially on imaginary radial plane 14,the torques affecting the component parts are kept to a minimum.

What is claimed is:
 1. A pulley that is decoupled from the vibrations ofa crankshaft and that has an integrated viscous torsional vibrationdamper, including a flywheel, which is arranged in a damper housing thatis filled with a viscous medium and that can rotate relative to thehousing, as well as a bearing and a coupling made of rubber elasticmaterial for supporting the pulley with respect to the damper housing ina flexible manner in the circumferential direction of the pulley and soas to be capable of relative rotation, the pulley being assigned to theflywheel so as to be axially adjoining, wherein the damper housing (5)has at least one first axial projection (8), which is enclosed by thebelt-bearing surface (9) of the pulley (1) at a radial clearance, andthe bearing (6) is arranged in the gap (10) that is formed by theclearance.
 2. The pulley as recited in claim 1, wherein the first axialprojection (8) constitutes an integral component part of the damperhousing (5).
 3. The pulley as recited in one of claims 1 through 2,wherein the pulley (1)—viewed in cross-section—has an essentiallyC-shaped profile.
 4. The pulley as recited in one of claims 1 through 3,wherein the bearing (6) is configured as a radial bearing.
 5. The pulleyas recited in one of claims 1 through 3, wherein the bearing isconfigured as a combined radial and axial bearing.
 6. The pulley asrecited in one of claims 1 through 5, wherein the bearing (6) isconfigured as an unlubricated sliding bearing.
 7. The pulley as recitedin one of claims 1 through 6, wherein the pulley (1) is connected viathe coupling (7) to the damper housing (5).
 8. The pulley as recited inone of claims 1 through 7, wherein the coupling (7), on the sideradially facing away from the pulley (1), is fixedly arranged on asecond axial projection (12) of the damper housing (5).
 9. The pulley asrecited in one of claims 1 through 8, wherein the belt-bearing surface(9), the bearing (6), the first axial projection (8), and the coupling(7) are arranged, in each case, so as to be concentric with regard toeach other.
 10. The pulley as recited in one of claims 1 through 9,wherein, for ventilating the interior space (16), openings (17, 18) areprovided in the damper housing (5) and in the pulley (1).